time-to-botec/js/node_modules/@stdlib/stats/base/maxabs/README.md

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# maxabs

> Calculate the maximum absolute value of a strided array.

<section class="intro">

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var maxabs = require( '@stdlib/stats/base/maxabs' );
```

#### maxabs( N, x, stride )

Computes the maximum absolute value of a strided array `x`.

```javascript
var x = [ 1.0, -2.0, 2.0 ];
var N = x.length;

var v = maxabs( N, x, 1 );
// returns 2.0
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
-   **stride**: index increment for `x`.

The `N` and `stride` parameters determine which elements in `x` are accessed at runtime. For example, to compute the maximum absolute value of every other element in `x`,

```javascript
var floor = require( '@stdlib/math/base/special/floor' );

var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ];
var N = floor( x.length / 2 );

var v = maxabs( N, x, 2 );
// returns 4.0
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

```javascript
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var N = floor( x0.length / 2 );

var v = maxabs( N, x1, 2 );
// returns 4.0
```

#### maxabs.ndarray( N, x, stride, offset )

Computes the maximum absolute value of a strided array using alternative indexing semantics.

```javascript
var x = [ 1.0, -2.0, 2.0 ];
var N = x.length;

var v = maxabs.ndarray( N, x, 1, 0 );
// returns 2.0
```

The function has the following additional parameters:

-   **offset**: starting index for `x`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the maximum absolute value for every other value in `x` starting from the second value

```javascript
var floor = require( '@stdlib/math/base/special/floor' );

var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];
var N = floor( x.length / 2 );

var v = maxabs.ndarray( N, x, 2, 1 );
// returns 4.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If `N <= 0`, both functions return `NaN`.
-   Depending on the environment, the typed versions ([`dmaxabs`][@stdlib/stats/base/dmaxabs], [`smaxabs`][@stdlib/stats/base/smaxabs], etc.) are likely to be significantly more performant.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var Float64Array = require( '@stdlib/array/float64' );
var maxabs = require( '@stdlib/stats/base/maxabs' );

var x;
var i;

x = new Float64Array( 10 );
for ( i = 0; i < x.length; i++ ) {
    x[ i ] = round( (randu()*100.0) - 50.0 );
}
console.log( x );

var v = maxabs( x.length, x, 1 );
console.log( v );
```

</section>

<!-- /.examples -->

<section class="links">

[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[@stdlib/stats/base/dmaxabs]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dmaxabs

[@stdlib/stats/base/smaxabs]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/smaxabs

</section>

<!-- /.links -->